H. L. Fairchild, « Animal self-defense » ,The Popular Science Monthly, septembre, vol. 21, n° 37, Londres, 1882, p. 603.
But many small creatures build individual shells or cases wholly for defense against ennemies. These are frequently carried about with the creature, as armor, wherever it goes. A familiar example, found in any brooklet, is seen in the case of the young caddis-fly. To hide and protect itself from the ever-hungry fishes, the larva of this insect incloses its body in a tube formed by gluing together bits of wood, shells, sand, and all sorts of matter that may be found at the bottom of a stream. This case has a silken lining, and out of the end the larva protrudes the its head and legs for locomotion, or wholly withdraws out of sight and danger.